Measurements and Modeling of Net Carbon Exchange over Southeastern Loblolly
Pine Plantation at the Duke Forest AmeriFlux Site
Sponsored by: Southeast Regional Center, National
Institute for Global Environmental Change (NIGEC)
The AmeriFlux
network goal is to generate data sets that include net CO2 exchange, and
associated physical and physiological parameters that are used to explain
spatial and temporal variation in net carbon exchange over dominant ecosystems.
The forest dominated by loblolly pine (Pinus taeda L.) is among the
most extensive in the Southeast, and loblolly pine is the most planted species
in the United States. We monitor net CO2 exchange at the Duke Forest
AmeriFlux site year-round over a 16.5 m tall, even-aged loblolly pine plantation.
These measurements are accompanied by measurements of ecological variables
(including leaf area index, vertical distribution of leaf area density, sap
flux, canopy conductance, canopy skin temperature), atmospheric variables
(including eddy-covariance water vapor, sensible heat, and momentum fluxes,
velocity statistics, air temperature, water vapor concentration and vapor
pressure deficit, CO2 concentration profiles inside and above the canopy,
photosynthetically active radiation (PAR), net radiation), and soil variables
(including soil physical characteristics, soil moisture, soil temperature,
soil water potential, and CO2 flux). The measurements (Beginning August
- 1997) are available at the
Duke Forest AmeriFlux site.
Additional ongoing studies at this site provide a full complement of all
core and suggested measurements in the AmeriFlux Science Plan. These
measurements are used to describe the relationship between ecosystem net
CO2 exchange and environmental variables measured above the canopy (e.g.,
PAR, VPD). We developed a turbulent transport model that can partition eddy
covariance measured fluxes above the canopy into vertical sources and sinks
within the canopy for the Duke Forest AmeriFlux pine site. This permits
detailed understanding of the effect of physical, physiological, and structural
canopy variables on carbon exchange at different layers within the forest
canopy. With this model, the impact of annual variability in climate
and large seasonal variation in leaf area density (and, in turn, light penetration,
atmospheric stability, and leaf physiology) on net ecosystem carbon exchange
can be explicitly quantified. With support from the
Terrestrial Carbon Processes (TCP) Program of DOE, we monitor the same
variables and quantify mass and energy exchanges between the biosphere and
atmosphere of two additional ecosystems adjacent to the pine plantation: (1)
an abandoned old field, and (2) an 80-year-old oak-hickory forest. This, in
combination with the NIGEC supported
measurements at the pine forest, comprises a unique AmeriFlux site in which
the three major stages of succession, as well as the three most dominating
vegetation types in one region, are evaluated for responses to the same atmospheric,
hydrologic and edaphic forcing.
Data
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